NCERT Exemplar Class 11 Biology Solutions for Chapter 9 Biomolecules

The NCERT Exemplar for Class 11 Biology Chapter 9 Biomolecules provides you with the necessary tool required to prepare well for the CBSE Class 11 and entrance examinations, like NEET. This solution is vital for a clear understanding of the topic from the examination point of view.

The NCERT Exemplar for Class 11 Biology Chapter 9 Biomolecules PDF provides answers to the chapter Biomolecules Class 11 NCERT questions, given in the exemplar book, along with Biomolecules essay questions, Biomolecules important questions, Biomolecules question bank, Biomolecules previous years’ questions for the NEET, Biomolecules MCQ GNEET, and tips and tricks.

Download the NCERT Exemplar for Class 11 Biology Chapter 9 Biomolecules PDF


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Access Answers to the NCERT Exemplar Solution for Class 11 Biology Chapter 9


1. It is said that the elemental composition of living organisms and that of

inanimate objects (like earth’s crust) are similar in the sense that all the

major elements are present in both. Then what would be the difference

between these two groups? Choose the correct answer from among the


a. Living organisms have more gold in them than inanimate objects

b. Living organisms have more water in their body than inanimate


c. Living organisms have more carbon, oxygen and hydrogen per

unit mass than inanimate objects.

d. Living organisms have more calcium in them than inanimate



Option (c) is the answer.

2. Many elements are found in living organisms either free or the form of

compounds. Which of the following is not found in living organisms?

a. Silicon

b. Magnesium

c. Iron

d. SodiumSolution:

Option (a) is the answer.

3. Aminoacids have both an amino group and a carboxyl group in their

structure. Which one of the following is an amino acid?

a. Formic acid

b. Glycerol

c. Glycolic Acid

d. Glycine


Option (d) is the answer.

4. An amino acid under certain conditions has both positive and negative

charges simultaneously in the same molecule. Such a form of amino acid

is called

a. Acidic form

b. Basic form

c. Aromatic form

d. Zwitterionic form


Option (d) is the answer.

5. Sugars are technically called carbohydrates, referring to the fact that

their formulae are only multiple of C(H2O). Hexoses, therefore, have six

carbons, twelve hydrogens and six oxygen atoms. Glucose is a hexose.

Choose from among the following another hexose.

a. Fructose

b. Erythrose

c. Ribulose

d. Ribose


Option (a) is the answer.

6. When you take cells or tissue pieces and grind them with an acid in a

mortar and pestle, all the small biomolecules dissolve in the acid.

Proteins, polysaccharides and nucleic acids are insoluble in mineral acid

and get precipitated. The acid-soluble compounds include amino acids,

nucleosides, small sugars etc. When one adds a phosphate group to a

nucleoside, one gets another acid-soluble biomolecule called

a. Nitrogen base

b. Adenine

c. Sugar phosphate

d. Nucleotide


Option (d) is the answer.

7. When we homogenise any tissue in acid the acid-soluble pool


a. Cytoplasm

b. Cell membrane

c. Nucleus

d. Mitochondria


Option (a) is the answer.

8. The most abundant component of living organisms is

a. Protein

b. Water

c. Sugar

d. Nucleic acid


Option (b) is the answer.

9. A homopolymer has only one type of building block called monomer

repeated ‘n’ number of times. A heteropolymer has more than one type

of monomer. Proteins are heteropolymers usually made ofa. 20 types of monomers

b. 40 types of monomers

c. 30 types of monomers

d. only one type of monomer


Option (a) is the answer

10. Proteins perform many physiological functions. For example, some

functions as enzymes. Which of the following represents an additional

function that some proteins discharge?

a. Antibiotics

b. Pigment conferring colour to skin

c. Pigments making colours of flowers

d. Hormones


Option (d) is the answer.

11. Glycogen is a homopolymer made of

a. Glucose units

b. Galactose units

c. Ribose units

d. Aminoacids


Option (a) is the answer.

12. The number of ‘ends’ in a glycogen molecule would be

a. Equal to the number of branches plus one

b. Equal to the number of branch points

c. One

d. Two, one on the left side and another on the right side


Option (d) is the answer.

13. The primary structure of a protein molecule has

a. Two ends

b. One end

c. Three ends

d. No ends


Option (a) is the answer.

14. Enzymes are biocatalysts. They catalyse biochemical reactions. In general,

they reduce the activation energy of reactions. Many Physico-chemical

processes are enzyme-mediated. Which of the following reactions is not

enzyme-mediated in the biological system?

a. Dissolving CO2 in water

b. Untwining the two strands of DNA

c. Hydrolysis of sucrose

d. Formation of peptide bond


Option (a) is the answer.


1. Medicines are either man-made (i.e., synthetic) or obtained from living

organisms like plants, bacteria, animals etc. and hence the latter are

called natural products. Sometimes natural products are chemically

altered by man to reduce toxicity or side effects. Write against each of

the following whether they were initially obtained as a natural product

or as a synthetic chemical.

a. Penicillin ___________________________

b. Sulfonamide ___________________________

c. Vitamin C ___________________________

d. Growth Hormone ___________________________


A. Penicillin- Natural product (obtained from fungus P. notatum)

B. sulphonamide- Synthetic product

C. Vitamin C- Natural product

D. Growth Hormone- Natural product

2. Select an appropriate chemical bond among ester bond, glycosidic bond, peptide bond and hydrogen bond and write against each of the following.

a. Polysaccharide ___________________________

b. Protein ___________________________

c. Fat ___________________________

d. Water ___________________________


a. Polysaccharides – Glycosidic bond, formed by elimination of water molecule.

b. Protein- peptide bond, it is the -CO-NH- BOND formed by elimination of water molecules.

c. Fats- ester bond, derived from an acid (organic or inorganic) in which at least one –OH (hydroxyl) group is replaced by an –O–alkyl (alkoxy) group

d. Water- H-bond, formed between the hydrogen of one water molecule and oxygen of the other water molecule.

3. Write the name of anyone amino acid, sugar, nucleotide and fatty acid.


Amino acid- Glycine

Sugar- Glucose

Nucleotide- Adenosine

Fatty acid- Oleic acid

4. The reaction given below is catalysed by oxidoreductase between two substrates A and A’, complete the reaction. A reduced + A’ oxidized


A[reduced] + A’[Oxidized] → A[oxidized] + A’[reduced]

5. How are prosthetic groups different from co-factors?


Cofactors are the no proteinous, may be organic or inorganic constituent of the enzyme. The prosthetic group belongs to organic cofactors, remains tightly bound with apoenzymes.

6. Glycine and Alanine are different with respect to one substituent on the α -carbon. What are the other common substituent groups?


-COOH, -NH2, and –H are the common substituents.

7. Starch, Cellulose, Glycogen, Chitin are polysaccharides found among the following. Choose the one appropriate and write against each.

Cotton fibre __________________________

Exoskeleton of cockroach __________________________

Liver __________________________

Peeled potato __________________________


Cotton fibre- cellulose [more than 90%].

The exoskeleton of cockroach- chitin

Liver- glycogen

Peeled potato- starch


1. Enzymes are proteins. Proteins are long chains of amino acids linked to

each other by peptide bonds. Aminoacids have many functional groups

in their structure. These functional groups are, many of them at least,

ionisable. As they are weak acids and bases in chemical nature, this

ionization is influenced by the pH of the solution. For many enzymes, activity

is influenced by the surrounding pH. This is depicted in the curve below,

explain briefly.

NCERT Exemplar Solutions of Class 11 Biology Chapter 9 Biomolecules-1


The dependence of enzyme on pH is due to the presence of charged amino acid at its active site, variation causes changes in charge of amino acid. The enzymatic activity decreases when pH is less than the optimum pH.

2. Is rubber a primary metabolite or a secondary metabolite? Write four sentences about rubber.


Rubber is secondary metabolite because the of its unknown function in plants physiology

It is obtained from plant as exude which is sticky

Rubber is used for synthesizing tyre, eraser etc.

3. Schematically represent primary, secondary and tertiary structures of a hypothetical polymer say for example a protein


NCERT Exemplar Solutions of Class 11 Biology Chapter 9 Biomolecules-2

4. Nucleic acids exhibit secondary structure, justify with example.


DNA and RNA are known to exist in the form of a helix. DNA forms double helix and RNA forms a single-stranded helical form. As helix is considered to be a secondary structure, therefore, nucleic acids exist in secondary structure.

5. Comment on the statement “living state is a non-equilibrium steady-state to be able to perform work”.


In a biological system, metabolic reactions always remain on and influx and efflux of metabolites take place constantly, hence it can be said that living state is a non-equilibrium steady state which can perform work.


1. Formation of the enzyme-substrate complex (ES) is the first step in catalysed reactions. Describe the other steps until the formation of the product.


1. In the first step, the substrate binds to the active site of the enzyme which fits into the active site

2. The binding of the substrate will help the enzyme to alter its shape and will fit more tightly

3. The active site of the enzyme breaks the chemical bond of the substrate thus forming a new enzyme product

4. The product will be released by the enzymes in the reaction and the free enzyme is ready to bind the substrate of another molecule and once again run through the catalytic cycle.

2. What are the different classes of enzymes? Explain any two with the type of reaction they catalyse.


There are different classes of enzymes. They are Oxidoreductase, Transferase, Hydrolase, Lysates, Isomerase, ligases.

a) Oxidoreductase:

These are the enzymes which help in simultaneous oxidation and reduction of two substrates.

S reduced + S’reduced → S oxidized + S’ oxidized

b) Hydrolases:

These enzymes facilitate the hydrolysis of a molecule.

Sucrose → Glucose + Fructose

3. Nucleic acids exhibit secondary structure. Describe through Watson Crick Model.


DNA is made up of two polypeptide chains, arranged in a double helix. The backbone is of sugar-phosphate while the nitrogenous bases are present on the inner side. These nitrogenous bases pairs to each other by H bonds. This H bond confers for the stability of helix.

NCERT Exemplar Solutions of Class 11 Biology Chapter 9 Biomolecules-3

4. What is the difference between a nucleotide and nucleoside? Give two examples of each with their structure.


Nucleotides are the monomers of nucleic acid and are formed of nucleoside and phosphate group. Whereas nucleosides are the constituent of nucleotides. Adenosine, guanosine, thymidine, uridine and cytidine are nucleosides. Adenylic acid, thymidylic acid, guanylic acid, uridylic acid and cacodylic acid are nucleotides.

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5. Describe various forms of lipid with a few examples.


Lipids are classified into three categories:

Simple lipids, compound lipids and derivatives.

Simple lipids are the esters of fatty acids eg: Triglycerol, fats and wax

Compound lipids are with an additional group other than fats and alcohols. An example is phospholipids, glycolipids

When lipids consist of hydrocarbon ring and the long chain of hydrocarbons they are called derivatives

Examples of Steroids, Cholesterol.

Biomolecules can be defined as molecules present in different organisms, which are responsible for a whole host of biological processes. Different processes, such as cell division and development, are run by biomolecules. Some types of biomolecules are as follows.

  1. Metabolites
  2. Hormones
  3. Neurotransmitters
  4. Vitamins
  5. Lipids and Fatty acids
Also Access 
NCERT Solutions for Class 11 Biology Chapter 9
CBSE Notes for Class 11 Biology Chapter 9

Important Topics of Chapter 9 Biomolecules

    1. Analysing Chemical Composition?
    2. Primary and Secondary Metabolites
    3. Bio-macromolecules
    4. Proteins
    5. Polysaccharides
    6. Nucleic Acids
    7. Structure of Proteins
    8. Nature of Bond Linking Monomers in a Polymer
    9. Dynamic State of Body Constituents – Concept of Metabolism
    10. Metabolic Basis for Living
    11. The Living State
    12. Enzymes

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